Divergent foraging strategies may emerge within a population due to a combination of physiological and environmental factors; yet to persist, neither strategy should offer a consistent selective advantage over the alternative in the long term. Murphy’s petrels Pterodroma ultima from Henderson Island (24°20′S, 128°20′W) in the South Pacific Ocean are highly vagile, and exhibit two distinct foraging trip types during incubation; similar proportions of birds undertake either looping trips around the South Pacific Gyre to waters off Peru (hereafter “East”) or trips south-west of the colony towards the Subtropical Front (“South”) (mean maximum ranges of c. 3800 or 2000 km from the colony, respectively). However, the relative benefits of the distinct trip types remain unclear. Through tracking birds with GPS and salt-water immersion loggers in 2015, the fine-scale foraging behaviour was examined for East (trip durations: 14.1–19.8 days, maximum ranges 2387–4823 km) and South trips (12.9–25.8 days, 1565–1991 km). Data on behaviour classified from GPS tracks, the number of wet bouts per hour (a proxy for landing rates) and wind speeds, were used to distinguish two distinct foraging modes: birds on East trips spent more time in directed movement, whereas those on South trips spent a greater proportion of time in area-restricted search (ARS) behaviour. East trips were associated with higher overall mass gain, and wet bouts occurred in equal proportions during directed movement and ARS behaviour. This suggests that in unproductive marine environments, it may be more profitable to maximise area covered to increase the chances of encountering prey. Analysis of lower-resolution geolocator data (collected from 2011 to 2014) indicated that individuals were largely consistent in trip type between years. Since birds that conducted East trips were 19% lighter on departure from the colony and experienced more frequent tailwinds on foraging trips, we speculate that these birds may benefit from reduced movement costs, whilst also experiencing reduced competition for foraging opportunities.

中文翻译：

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一种异常广泛的海鸟墨菲海燕孵化过程中的不同觅食策略

由于生理和环境因素的共同作用，种群中可能会出现不同的觅食策略；然而，从长远来看，这两种战略都不应该提供持续的选择优势。来自南太平洋亨德森岛 (24°20′S, 128°20′W) 的墨菲海燕 Pterodroma ultima 高度游荡，在孵化过程中表现出两种截然不同的觅食旅行类型；相似比例的鸟类要么绕着南太平洋环流环游到秘鲁附近的水域（下称“东”），要么从殖民地西南方向前往亚热带锋（“南”）（平均最大范围约为 3800 年或 2000 年）距殖民地公里）。然而，不同旅行类型的相对好处仍不清楚。通过在 2015 年使用 GPS 和盐水浸入式记录仪跟踪鸟类，检查了东部（旅行持续时间：14.1-19.8 天，最大范围 2387-4823 公里）和南部旅行（12.9-25.8 天，1565-1991 公里）的精细觅食行为。从 GPS 轨迹分类的行为数据、每小时潮湿的次数（着陆率的代表）和风速，被用来区分两种不同的觅食模式：东部旅行的鸟类在定向运动上花费的时间更多，而南部旅行的鸟类在旅行在区域限制搜索 (ARS) 行为中花费的时间比例更大。东部旅行与更高的整体质量增加有关，并且在定向运动和 ARS 行为期间，湿性发作的发生比例相等。这表明在非生产性的海洋环境中，最大化覆盖面积以增加遇到猎物的机会可能更有利可图。对低分辨率地理定位器数据（从 2011 年到 2014 年收集）的分析表明，个人在不同年份的旅行类型上基本一致。由于进行东部旅行的鸟类在离开殖民地时体重减轻了 19%，并且在觅食旅行时遇到了更频繁的顺风，我们推测这些鸟类可能会受益于降低的移动成本，同时也减少了对觅食机会的竞争。